So far, for example, Patent Document 1 discloses an internal combustion engine having a turbo-supercharger which includes a centrifugal compressor. This conventional internal combustion engine is provided with an EGR passage for recirculating recirculated exhaust gas (EGR gas) to an intake passage on the upstream side of the compressor from an exhaust system.
Including the above described document, the applicant is aware of the following documents as related art of the present invention.
If the EGR gas is introduced into an intake system from a section near the inlet of a compressor as in the internal combustion engine described in Patent Document 1, a high-temperature section is locally generated inside the compressor due to a lack of mixing of high-temperature EGR gas and low-temperature (ordinary temperature) fresh air. If blow-by gas is introduced into the intake system from a section near the inlet of the compressor in a situation in which the high-temperature section exists locally inside the compressor as described above, misty oil included in the blow-by gas comes into contact with the aforementioned high-temperature section, and, thereby, deposits may be produced and collected at section inside the compressor, such as its diffuser section. If such collection of the deposits progresses, there is a concern that performance degradation of the turbo-supercharger may occur.